U.S. patent application number 14/219521 was filed with the patent office on 2015-07-02 for apparatus and method of determining optimal energy window for optimal positron emission tomography.
This patent application is currently assigned to KOREA INSTITUTE OF RADIOLOGICAL & MEDICAL SCIENCES. The applicant listed for this patent is KOREA INSTITUTE OF RADIOLOGICAL & MEDICAL SCIENCES. Invention is credited to Gwang Il AN, Hee-Joung KIM, Jin Su KIM, Kyeong Min KIM, Sang-Moo LIM, A Ram YU.
Application Number | 20150185338 14/219521 |
Document ID | / |
Family ID | 53441725 |
Filed Date | 2015-07-02 |
United States Patent
Application |
20150185338 |
Kind Code |
A1 |
KIM; Jin Su ; et
al. |
July 2, 2015 |
APPARATUS AND METHOD OF DETERMINING OPTIMAL ENERGY WINDOW FOR
OPTIMAL POSITRON EMISSION TOMOGRAPHY
Abstract
An apparatus and method for determining an optimal energy window
for optimal positron emission tomography (PET) is disclosed. An
optimal energy window determining apparatus may include a data
corrector configured to correct data measured from an image quality
phantom, an image quality measurer configured to measure an image
quality for the corrected data, and an optimal energy window
determiner configured to determine the optimal energy window based
on the measured image quality. The data corrector may correct the
measured data based on a difference between sensitivities measured
using different radiopharmaceuticals in at least one energy
window.
Inventors: |
KIM; Jin Su; (Seoul, KR)
; YU; A Ram; (Seoul, KR) ; KIM; Hee-Joung;
(Wonju-si, KR) ; LIM; Sang-Moo; (Seoul, KR)
; KIM; Kyeong Min; (Seoul, KR) ; AN; Gwang Il;
(Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA INSTITUTE OF RADIOLOGICAL & MEDICAL SCIENCES |
Seoul |
|
KR |
|
|
Assignee: |
KOREA INSTITUTE OF RADIOLOGICAL
& MEDICAL SCIENCES
Seoul
KR
|
Family ID: |
53441725 |
Appl. No.: |
14/219521 |
Filed: |
March 19, 2014 |
Current U.S.
Class: |
250/252.1 |
Current CPC
Class: |
G01T 1/1647
20130101 |
International
Class: |
G01T 1/29 20060101
G01T001/29 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2013 |
KR |
10-2013-0163677 |
Claims
1. An apparatus for determining an optimal energy window in
positron emission tomography (PET), the apparatus comprising: a
data corrector configured to correct data measured from an image
quality phantom, wherein the measured data comprises a single gamma
photon; an image quality measurer configured to measure an image
quality for the corrected data; and an optimal energy window
determiner configured to determine the optimal energy window based
on the measured image quality, wherein the data corrector is
configured to correct the measured data based on a difference
between a first sensitivity of a first radiopharmaceutical and a
second sensitivity of a second radiopharmaceutical in at least one
energy window.
2. The apparatus of claim 1, wherein the data corrector is
configured to correct the measured data based on a single gamma
photon fraction (SGF), and wherein the SGF is calculated according
to the following equation 1, S G F = the first sensitivity - the
second sensitivity the first sensitivity . [ Equation 1 ]
##EQU00004##
3. The apparatus of claim 2, wherein the data corrector is
configured to correct the single gamma photon by calculating a
corrected sonogram according to the following equation 2, Corrected
sonogram=a measured sonogram-a scatter component.times.a background
scale factor, [Equation 2] and wherein the background scale factor
is calculated according to the following equation 3 Background
scale factor=1-SGF. [Equation 3].
4. The apparatus of claim 1, wherein the image quality measurer is
configured to measure at least one of non-uniformity (NU)
information, recovery coefficient (RC) information, and a spill
over ratio (SOR) from the corrected data.
5. The apparatus of claim 1, wherein the optimal energy window
determiner is configured to calculate a figure of merit (FOM) based
on the measured image quality, and to determine the optimal energy
window having a smallest value of the FOM, wherein the FOM is
calculated according to the following equation 4, F O M = f air
.times. SOR air 2 + f water .times. SOR water 2 .times. N U
Sensitivity RC 1 2 + RC 2 2 + RC 3 2 + RC 4 2 + RC 5 2 , [ Equation
4 ] ##EQU00005## wherein NU denotes non-uniformity information
measured from the corrected data, wherein the sensitivity denotes
sensitivity information of the corrected data, wherein a spill over
ratio of air (SOR.sub.air) denotes recovery coefficient (RC)
information measured from air and a spill over ratio of water
(SOR.sub.water) denotes RC information measured from water among a
plurality of sets of RC information, and wherein RC.sub.1 to
RC.sub.5 denote different sets of RC information measured from
different energy window.
6. The apparatus of claim 1, wherein the optimal energy window
determiner is configured to calculate a figure of merit (FOM based
on non-uniformity (NU) information, recovery coefficient (RC)
information, and a spill over ratio (SOR) measured from the
corrected data by the image quality measurer.
7. A method of determining an optimal energy window in positron
emission tomography (PET), the method comprising: correcting, by a
data corrector, data measured from an image quality phantom,
wherein the measured data comprises a single gamma photon;
measuring, by an image quality measurer, an image quality for the
corrected data; and determining, by an optimal energy window
determiner, the optimal energy window based on the measured image
quality, wherein the correcting of the measured data comprises
correcting the measured data based on a difference between a first
sensitivity of a first radiopharmaceutical and a second sensitivity
of a second radiopharmaceutical in at least one energy window.
8. The method of claim 7, wherein the correcting of the measured
data comprises: calculating the difference value between the first
sensitivity measured using the first radiopharmaceutical and the
second sensitivity measured using the second radiopharmaceutical;
and calculating a single gamma photon fraction (SGF), wherein the
SGF is calculated according to the following equation 1, S G F =
the first sensitivity - the second sensitivity the first
sensitivity . [ Equation 1 ] ##EQU00006##
9. The method of claim 8, wherein the correcting of the measured
data comprises correcting the single gamma photon by calculating a
corrected sonogram according to the following equation 2, Corrected
sonogram=a measured sonogram-a scatter component.times.a background
scale factor, [Equation 2] and wherein the background scale factor
is calculated according to the following equation 3 Background
scale factor=1-SGF [Equation 3].
10. The method of claim 7, wherein the measuring of the image
quality comprises measuring at least one of non-uniformity (NU)
information, recovery coefficient (RC) information, and a spill
over ratio (SOR) from the corrected data.
11. The method of claim 7, wherein the determining of the optimal
energy window determiner comprises: calculating a figure of merit
(FOM) based on the measured image quality; and determining the
optimal energy window having a smallest value of the FOM, wherein
the FOM is calculated according to the following equation 4, F O M
= f air .times. SOR air 2 + f water .times. SOR water 2 .times. N U
Sensitivity RC 1 2 + RC 2 2 + RC 3 2 + RC 4 2 + RC 5 2 , [ Equation
4 ] ##EQU00007## wherein NU denotes non-uniformity information
measured from the corrected data, wherein the sensitivity denotes
sensitivity information of the corrected data, wherein a spill over
ratio of air (SOR.sub.air) denotes recovery coefficient (RC)
information measured from air and a spill over ratio of water
(SOR.sub.water) denotes RC information measured from water among a
plurality of sets of RC information, and wherein RC.sub.1 to
RC.sub.5 denote different sets of RC information measured from
different energy window.
12. The method of claim 7, wherein the determining of the optimal
energy window determiner comprises: calculating a figure of merit
(FOM based on non-uniformity (NU) information, recovery coefficient
(RC) information, and a spill over ratio (SOR) measured from the
corrected data.
13. A non-transitory computer-readable recording medium storing a
program to implement a method of determining an optimal energy
window in positron emission tomography (PET), the method
comprising: correcting, by a data corrector, data measured from an
image quality phantom, wherein the measured data comprises a single
gamma photon; measuring, by an image quality measurer, an image
quality for the corrected data; and determining, by an optimal
energy window determiner, the optimal energy window based on the
measured image quality, wherein the correcting of the measured data
comprises correcting the measured data based on a difference
between a first sensitivity of a first radiopharmaceutical and a
second sensitivity of a second radiopharmaceutical in at least one
energy window.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Korean
Patent Application No. 10-2013-0163677, filed on Dec. 26, 2013, in
the Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a technology for
determining an optimal energy window to determine settings for
optimal positron emission tomography (PET).
[0004] 2. Description of the Related Art
[0005] Positron emission tomography (PET) refers to one of nuclear
medicine test technologies for injecting, into a human body,
radiopharmaceuticals emitting positrons and reconfiguring, using an
exclusive scanner, a shape of the injected radiopharmaceuticals
used in the human body.
[0006] In general, such PET has been adopted to diagnose various
types of cancers and also has been known as an efficient test to
perform a differential diagnosis on a cancer, clinical staging, an
evaluation of recurrence, and a determination as to the treatment
effect. In addition, a receptor image or a metabolic image used for
evaluating heart disease, brain disease, and brain functions may be
acquired using the PET.
[0007] Positrons may be emitted from radioactive isotopes, such as,
C-11, N-13, O-15, and F-18, as a kind of radiation. The radioactive
isotopes correspond to principal constituent components of a
biomaterial and thus, radiopharmaceuticals, that is, a tracer for
applying a predetermined change in physiological, chemical, and
functional views may be produced using the radioactive
isotopes.
SUMMARY
[0008] An embodiment provides an apparatus for determining an
optimal energy window in positron emission tomography (PET), the
apparatus including a data corrector configured to correct data
measured from an image quality phantom, an image quality measurer
configured to measure an image quality for the corrected data, and
an optimal energy window determiner configured to determine the
optimal energy window based on the measured image quality. The data
corrector may correct the measured data based on a difference
between sensitivities measured using different radiopharmaceuticals
in at least one energy window.
[0009] The data corrector may correct the measured data by
calculating a ratio of a first sensitivity to a difference value
between the first sensitivity measured using a first
radiopharmaceutical and a second sensitivity measured using a
second radiopharmaceutical.
[0010] The data corrector may correct the measured data by
subtracting, from the measured data, a value in which the
calculated ratio is applied to a scatter component corresponding to
the measured data.
[0011] The image quality measurer may measure at least one of
non-uniformity (NU) information, recovery coefficient (RC)
information, and a spill over ratio (SOR) from the corrected
data.
[0012] The optimal energy window determiner may calculate a figure
of merit (FOM) based on the measured image quality, and may
determine the optimal energy window based on the calculated
FOM.
[0013] The optimal energy window determiner may calculate the FOM
based on NU information, RC information, and an SOR measured from
the corrected data by the image quality measurer.
[0014] Another embodiment provides a method of determining an
optimal energy window in PET, the method including correcting, by a
data corrector, data measured from an image quality phantom,
measuring, by an image quality measurer, an image quality for the
corrected data, and determining, by an optimal energy window
determiner, the optimal energy window based on the measured image
quality. The correcting of the measured data may include correcting
the measured data based on a difference between sensitivities
measured using different radiopharmaceuticals in at least one
energy window.
[0015] The correcting of the measured data may include calculating
a difference value between a first sensitivity measured using a
first radiopharmaceutical and a second sensitivity measured using a
second radiopharmaceutical, calculating a ratio of the first
sensitivity to the calculated difference value, and correcting the
measured data based on the calculated ratio.
[0016] The correcting of the measured data based on the calculated
ratio may include correcting the measured data by subtracting, from
the measured data, a value in which the calculated ratio is applied
to a scatter component corresponding to the measured data.
[0017] The measuring of the image quality may include measuring at
least one of NU information, RC information, and an SOR from the
corrected data.
[0018] The determining of the optimal energy window determiner may
include calculating a FOM based on the measured image quality, and
determining the optimal energy window based on the calculated
FOM.
[0019] The determining of the optimal energy window determiner may
include calculating the FOM based on NU information, RC
information, and an SOR measured from the corrected data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] These and/or other aspects, features, and advantages of the
invention will become apparent and more readily appreciated from
the following description of exemplary embodiments, taken in
conjunction with the accompanying drawings of which:
[0021] FIG. 1 is a block diagram illustrating an optimal energy
window determining apparatus according to an embodiment.
[0022] FIG. 2 is a table describing a single gamma photon fraction
(SGF) according to an embodiment.
[0023] FIG. 3 is a diagram describing an image quality phantom
according to an embodiment.
[0024] FIGS. 4A, 4B, and 4C are graphs describing an embodiment of
performing a single gamma photon correction on data measured from
an image quality phantom according to an embodiment.
[0025] FIG. 5 illustrates an embodiment of correcting the single
gamma photon of FIG. 4.
[0026] FIG. 6 is a graph describing non-uniformity (NU) information
measured by an image quality measurer according to an
embodiment.
[0027] FIG. 7 is a graph describing recovery coefficient (RC)
information measured by an image quality measurer according to an
embodiment.
[0028] FIGS. 8A and 8B are graphs describing a spill over ratio
(SOR) measured by an image quality measurer according to an
embodiment.
[0029] FIG. 9 is a graph showing a decrease ratio of an SOR after a
single gamma photon correction is applied.
[0030] FIG. 10 is a table showing a figure of merit (FOM)
calculated for each energy window.
[0031] FIG. 11 is a flowchart illustrating an optimal energy window
determining method according to an embodiment.
DETAILED DESCRIPTION
[0032] Reference will now be made in detail to exemplary
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to like elements throughout. Exemplary embodiments
are described below to explain the present invention by referring
to the figures.
[0033] When it is determined detailed description related to a
related known function or configuration they may make the purpose
of the present invention unnecessarily ambiguous in describing the
present invention, the detailed description will be omitted here.
Also, terminologies used herein are defined to appropriately
describe the exemplary embodiments of the present invention and
thus, may be changed depending on a user, the intent of an
operator, or a custom. Accordingly, the terminologies must be
defined based on the following overall description of this
specification.
[0034] FIG. 1 is a block diagram illustrating an optimal energy
window determining apparatus 100 according to an embodiment.
[0035] The optimal energy window determining apparatus 100 may
determine an optimal energy window for positron emission tomography
(PET) through a data correction including a single gamma photon
correction.
[0036] To this end, the optimal energy window determining apparatus
100 may include a data corrector 110, an image quality measurer
120, and an optimal energy window determiner 130.
[0037] Specifically, the data corrector 110 may correct data
measured from an image quality phantom.
[0038] High-energy gamma photons may degrade an image quality.
Single gamma photons that may be classified into the high-energy
gamma photons may act as a background noise factor in reconfigured
PET. Thus, the single gamma photons need to be corrected to enhance
the image quality.
[0039] Data measured from the image quality phantom may include
single gamma photons. Thus, the data corrector 110 may correct the
measured data by correcting the single gamma photons.
[0040] The data corrector 110 may correct the measured data based
on a difference between sensitivities measured using different
radiopharmaceuticals in at least one energy window.
[0041] Specifically, to correct the measured data, the data
corrector 110 may calculate a difference value between a first
sensitivity measured using a first radiopharmaceutical and a second
sensitivity measured using a second radiopharmaceutical. The data
corrector 110 may calculate a ratio of the first sensitivity to the
calculated difference value, and may correct the measured data
based on the calculated ratio.
[0042] The calculated ratio may be defined as a single gamma photon
fraction (SGF).
[0043] Radioactive isotopes such as C-11, N-13, O-15, F-18, and
I-124 may be used as radiopharmaceuticals. An embodiment of
correcting measured data using radiopharmaceuticals of F-18 and
I-124 is described herein. However, it is only an example and thus,
various radiopharmaceuticals may be used in addition to the
radiopharmaceuticals of F-18 and I-124.
[0044] The data corrector 110 may use I-124 as the first
radiopharmaceutical and may use F-18 as the second
radiopharmaceutical.
[0045] More specifically, the data corrector 110 may calculate an
SGF according to Equation 1.
SGF = 124 Isensitivity - 18 Fsensitivity 124 Isensitivity [
Equation 1 ] ##EQU00001##
[0046] In Equation 1, .sup.124I sensitivity denotes the first
sensitivity measured from the image quality phantom using the
radiopharmaceutical of I-124, and .sup.18F sensitivity denotes the
second sensitivity measured from the image quality phantom using
the radiopharmaceutical of F-18.
[0047] The SGF is further described with reference to FIG. 2.
[0048] FIG. 2 is a table 200 describing an SGF according to an
embodiment.
[0049] The table 200 of FIG. 2 shows sensitivities measured in
energy windows of 350 to 550, 350 to 600, 350 to 650, 350 to 750,
390 to 550, and 400 to 590 keV, which are different energy bands,
and SGFs according thereto.
[0050] For example, SGFs may be calculated as expressed by Equation
2 by applying sensitivities measured in the energy band of 350 to
750 keV of the table 200. For reference, in the present embodiment,
a first sensitivity is "9.83" measured using the
radiopharmaceutical of I-124 in the energy band of 350 to 750 keV
and a second sensitivity is "6.81" measured using the
radiopharmaceutical of F-18 in the energy band of 350 to 750
keV.
SGF = 9.83 - 6.81 9.83 = 0.31 [ Equation 2 ] ##EQU00002##
[0051] Referring again to FIG. 2, the image quality measurer 120
may measure an image quality for the corrected data. Specifically,
the image quality measurer 120 may measure at least one of
non-uniformity (NU) information, recovery coefficient (RC)
information, and a spill over ratio (SOR) from the corrected
data.
[0052] The optimal energy window determiner 130 may determine the
optimal energy window based on the measured image quality. For
example, the optimal energy window determiner 130 may calculate a
figure of merit (FOM) based on the NU information, the RC
information, and the SOR measured from the corrected data, and may
determine the optimal energy window based on the calculated
FOM.
[0053] More specifically, the optimal energy window determiner 130
may calculate the FOM according to Equation 3.
FOM = f air SOR air 2 + f water SOR water 2 .times. NU Sensitivity
RC 1 2 + RC 2 2 + RC 3 2 + RC 4 2 + RC 5 2 [ Equation 3 ]
##EQU00003##
[0054] In Equation 3, NU denotes NU information measured from the
corrected data and sensitivity denotes sensitivity information.
Also, SOR.sub.air denotes RC information measured from the air and
SOR.sub.water denotes RC information measured from the water, among
a plurality of sets of RC information. In addition, RC.sub.1 to
RC.sub.5 denote different sets of RC information measured from
different energy windows, respectively.
[0055] For example, the optimal energy window determiner 130 may
determine, as an optimal energy window band, an energy window band
corresponding to a FOM having the smallest size among FOMs
calculated in different energy windows.
[0056] FIG. 3 is a diagram describing an image quality phantom 310
according to an embodiment.
[0057] The image quality phantom 310 may use F-18 and I-124 of 100
.mu.Ci as a source. Also, a scan time of I-124 may be set as 80
minutes, and a scan time of F-18 may be set as 20 minutes.
Accordingly, the image quality phantom may obtain data in different
energy windows, for example, 350 to 550, 350 to 600, 350 to 650,
350 to 750, 390 to 550, and 400 to 590 keV.
[0058] Also, an energy window-by-energy window SOR may be measured
using materials, such as the water and the air, on one side 320 of
the image quality phantom 310. Energy window-by-energy window RC
information may be measured using holes having different apertures
on another side 330 of the image quality phantom 310.
[0059] FIGS. 4A, 4B, and 4C are graphs 410, 420, and 430 describing
an embodiment of performing a single gamma photon correction on
data measured from an image quality phantom according to an
embodiment.
[0060] The graph 410 of FIG. 4A shows a shape in which data
measured from the image quality phantom is attenuated, and the
graph 420 of FIG. 4B shows a shape in which the measured data is
distorted due to attenuation and scattering. The graph 430 of FIG.
4C shows a single gamma photon formed based on the shape in which
the measured data is attenuated and distorted.
[0061] Single gamma photons may act as a background noise factor in
reconfigured PET. Accordingly, such single gamma photons need to be
corrected to enhance the image quality.
[0062] FIG. 5 illustrates an embodiment of correcting the single
gamma photon of FIG. 4.
[0063] A data corrector according to an embodiment may correct the
measured data by subtracting, from the measured data, a value in
which the calculated ratio, that is, an SGF is applied to a scatter
component corresponding to the measured data. A process of
correcting the measured data by subtracting, from the measured
data, the value in which the SGF is applied may be interpreted as a
single gamma photon correction.
[0064] For example, to correct the single gamma photon, the data
corrector may perform a correction by applying the calculated SGF
to a measured sinogram 510. The measured sinogram 510 may be
interpreted as information that is reconfigured from data measured
from the image quality phantom.
[0065] To this end, the data corrector may calculate a corrected
sinogram 530 with respect to the measured sinogram 510 according to
Equation 4.
Corrected sonogram=measured sinogram-scatter component*background
scale factor(=1-SGF) [Equation 4]
[0066] For example, if SGF "0.31" calculated in the energy band of
350 to 750 keV is used, "1-0.31=0.69" may be applied to "scatter
component" as "background scale factor" and a result of the
applying may be subtracted from "measured sinogram". That is, if
"scatter component*0.69" is subtracted from "measured sinogram", a
result of the subtracting may be "corrected sinogram" in the energy
window of 350 to 750 keV.
[0067] FIG. 6 is a graph 600 describing NU information measured by
an image quality measurer according to an embodiment.
[0068] The graph 600 shows NU information measured using I-124 and
F-18 in energy windows of 350 to 550, 350 to 600, 350 to 650, 350
to 750, 390 to 550, and 400 to 590 keV, which are different energy
bands.
[0069] The graph 600 shows NU information measured using I-124 and
NU information measured using F-18. Here, the NU information
measured using I-124 may be interpreted as information in which a
single gamma photon correction is applied using an SGF. Also, the
NU information measured using F-18 may be interpreted as
information in which only a scatter correction is applied.
[0070] As shown in the graph 600, NU information between about 6.3%
and about 7.3% may be measured.
[0071] FIG. 7 is a graph 700 describing RC information measured by
an image quality measurer according to an embodiment.
[0072] The image quality measurer according to an embodiment may
measure different sets of RC information based on a diameter of an
image quality phantom rod for each energy window. RC information
may increase according to an increase in the diameter of the image
quality phantom rod. However, a difference in RC information
according to a difference in an energy window may be
insignificant.
[0073] FIGS. 8A and 8B are graphs 810 and 820 describing an SOR
measured by an image quality measurer according to an
embodiment.
[0074] An SOR may be measured due to a material difference for rods
disposed on the same side of an image quality phantom. The graph
810 shows an SOR with respect to the air for each energy window,
and the graph 820 shows an SOR with respect to the water for each
energy window. Also, each SOR may be measured from data of I-124 in
which a single gamma correction is applied and data of F-18 in
which a scatter correction is applied.
[0075] FIG. 9 is a graph 900 showing a decrease ratio of an SOR
after a single gamma photon correction is applied.
[0076] A difference in an SOR may occur due to a single gamma
photon correction.
[0077] Referring to the graph 900, an SOR after the single gamma
photon correction is appeared was largest in the energy window of
350 to 750 keV and no significant difference in an SOR was found in
remaining energy windows.
[0078] FIG. 10 is a table 1000 showing a FOM calculated for each
energy window.
[0079] A box 1010 indicated by a dotted line represents FOMs in the
energy window of, for example, 350 to 750 keV among energy
windows.
[0080] Referring to the box 1010, an attenuation corrected (AC) FOM
was calculated as "86.98" and an attenuation corrected and scatter
corrected (AC&SC) FOM was calculated as "70.65" in the energy
window of 350 to 750 keV. A single gamma photon corrected FOM in
which an SGF is further applied to an attenuation correction and a
scatter correction was calculated as "64.64", which is lowest among
a total of FOMs in the table 1000.
[0081] Accordingly, the energy window of 350 to 750 keV may be
determined as the optimal energy window.
[0082] For reference, an FOM in an energy window may be calculated
according to Equation 3, which is described above with reference to
FIG. 1.
[0083] FIG. 11 is a flowchart illustrating an optimal energy window
determining method according to an embodiment.
[0084] In operation 1101, the optimal energy window determining
method may correct data measured from an image quality phantom.
Specifically, the optimal energy window determining method may
correct the data measured from the image quality phantom using a
data corrector.
[0085] For example, the optimal energy window determining method
may correct the measured data based on a difference between
sensitivities measured using different radiopharmaceuticals in at
least one energy window.
[0086] More specifically, the optimal energy window determining
method may calculate a difference value between a first sensitivity
measured using a first radiopharmaceutical and a second sensitivity
measured using a second radiopharmaceutical. The optimal energy
window determining method may calculate a ratio of the first
sensitivity to the calculated difference value, and may correct the
measured data based on the calculated ratio. As an example, the
optimal energy window determining method may correct the measured
data by subtracting, from the measured data, a value in which the
calculated ratio is applied to a scatter component corresponding to
the measured data.
[0087] In operation 1102, the optimal energy window determining
method may measure an image quality for the corrected data. For
example, the optimal energy window determining method may measure
at least one of NU information, RC information, and an SOR from the
corrected data.
[0088] In operation 1103, the optimal energy window determining
method may determine an optimal energy window based on the measured
image quality. The optimal energy window determining method may
determine the optimal energy window based on the measured image
quality using an optimal energy window determiner.
[0089] Specifically, the optimal energy window determining method
may calculate a FOM based on NU information, RC information, and an
SOR measured from the corrected data, and may determine the optimal
energy window based on the calculated FOM.
[0090] The above-described exemplary embodiments may be recorded in
non-transitory computer-readable media including program
instructions to implement various operations embodied by a
computer. The media may also include, alone or in combination with
the program instructions, data files, data structures, and the
like. Examples of non-transitory computer-readable media include
magnetic media such as hard disks, floppy disks, and magnetic tape;
optical media such as CD ROM disks and DVDs; magneto-optical media
such as floptical disks; and hardware devices that are specially
configured to store and perform program instructions, such as
read-only memory (ROM), random access memory (RAM), flash memory,
and the like. Examples of program instructions include both machine
code, such as produced by a compiler, and files containing higher
level code that may be executed by the computer using an
interpreter. The described hardware devices may be configured to
act as one or more software modules in order to perform the
operations of the above-described exemplary embodiments of the
present invention, or vice versa.
[0091] Although a few exemplary embodiments of the present
invention have been shown and described, the present invention is
not limited to the described exemplary embodiments. Instead, it
would be appreciated by those skilled in the art that changes may
be made to these exemplary embodiments without departing from the
principles and spirit of the invention, the scope of which is
defined by the claims and their equivalents.
* * * * *